The present invention relates to solar heating and cooling systems, and more particularly to a solar heating and cooling system having multiple operating modes.
Due to the energy crises presently existing and the increase in the price of fuel, the attention of engineers, inventors, and other has been directed to the utilization of alternate sources of energy such as solar heating and cooling systems. Solar collectors and heat exchanger units are the very heart of any solar heating and cooling system. If such an apparatus is to be mounted on the roof of a building, and particularly on a home, there are space limitations which must be considered. Thus, if the installation is too bulky and occupies an excessive amount of space on the roof, it will not be acceptable to the public. If the units are especially massive or heavy, they are not susceptible of installation on presently existing buildings without making major structural changes to the buildings. The apparatus which is installed on a roof should be of compact thickness and occupy as small an area as possible to avoid an unsightly appearance.
Further, solar heating and cooling systems should be capable of various modes of operation to take advantage of various heating and cooling energies when those energies are readily available, and should further be capable of supplying different types of conditioned air when appropriate.
Solar heating and cooling systems now available to the public are very expensive from both construction and installation standpoints, with the total costs being excessively high so as to discourage their acceptance. The present invention is founded on the belief that the system of this invention may be manufactured and installed at a price which will be acceptable to many of the people who cannot now afford the existing solar heating and cooling systems. In addition, the operational costs will be a fraction of that of the conventional heating and cooling systems. One of the outstanding features of the instant system is that it may be installed in most existing building structures with minimal alterations thereof and without disrupting the present heating and/or cooling systems. The system of the present invention does not require that a new building or home be constructed to accommodate it, thus making this system readily available to the public.
Conventional heating and cooling systems, and many of the known solar heating and cooling systems are notably lacking in means for the storage of thermal energy and thus are forced to operate on what may be called a demand basis, and such techniques result in wasted and inefficient utilization thereof.
The problems resulting from the demand basis technique may be placed in three major problem areas with the first being demand timing, the second being the intermittent delivery, and the third problem being the fluctuating amounts of energy that must be supplied to satisfy the demand.
To explain the term `demand basis`, consider a home which is either too hot or too cold, that fact is sensed by a thermostat which actuates the appropriate equipment and when that demand has been satisfied, the equipment is shut down.
With regard to the first problem area defined above as `demand timing`, the demand for heating and/or cooling invariably occurs at times when those tasks are most inefficiently accomplished. For example, it is well known that a heat pump is an efficient mechanism, however, the demand basis under which a heat pump is forced to operate substantially reduces the efficiency of that equipment. During a heating cycle, the heat pump will extract heat from the atmosphere and direct it to the zone being heated. The demand for heat in the zone is the greatest when the temperature is low and the atmosphere contains a relatively small amount of readily available heat. Due to this lack of readily available heat, during the peak demand time, the heat pump must work hard to accomplish the task being asked of it. The same basic inefficiency results during a cooling cycle of the heat pump due to the heat extracted from the zone being dissipated into the atmosphere that already contains a relatively large quantity of heat. Thus, to accomplish satisfactory operation under these conditions, the equipment must be relatively large to compensate for inefficient operation resulting from demand timing and it is readily apparent that operating the equipment inefficiently results in the consumption of power at a rate which is excessive for the amount of work being accomplished.
In regard to the second problem defined above as `intermittent delivery`, consider a zone being heated with the thermostat being set at 70.degree.. Due to intermittent delivery, the temperature in the zone will vary in a range of from about 67.degree. to 74.degree.. When the temperature in the zone falls to about 67.degree., the heating equipment is started and will continue to operate until the zone temperature reaches about 74.degree. at which time the equipment is shut off. The temperature will then drop until the 67.degree. level is reached again and the heating cycle is repeated again. This temperature drop is non-linear due to the varying heat loss at the different temperatures, with the heat loss being considerably greater at 74.degree. than at the lower temperatures. It is well known that the heat loss through walls, ceilings, windows, and the like, is determined by the temperature differential on opposite sides thereof. Thus, the temperature drop from 74.degree. to 70.degree. will be relatively rapid and it will slow down in the drop from 70.degree. to 67.degree.. The zone will therefore fluctuate in temperature and will be below the desired 70.degree. level the greatest percentage of the time. It will be obvious that the exact opposite temperature fluctuations will occur when a zone is being cooled. Such temperature fluctuations in conjunction with the duration of the undesirable temperatures results in discomfort often resulting in upward or downward adjustments of the thermostat. Such discomfort is but one drawback of an intermittent delivery system with other drawbacks being the relatively high power consumption and the heat loss or gain of such a system when compared with one of constant delivery. The power consumed in repeatedly starting and stopping equipment is well known to be greater than the power consumed in continuous operation thereof. Also, repeated actuation of such equipment to raise or lower the temperature utilizes more energy than constantly deliverying constant properly conditioned air to maintain the desired temperature. By maintaining a constant confortable temperature, the increased heat loss or gain which occurs at fluctuating temperatures is avoided.
The third problem area relating to the fluctuating amounts of energy supplied to satisfy the demand basis technique will be easily understood upon consideration of the hereinbefore described examples relating to heating and cooling. It has been established that the demand for heating and cooling is the greatest when it is most difficult to accomplish those tasks. Those demands, plus other energy consuming habits of the consumers, cause tremendous fluctuation of the energy consumption to occur over a given period of time. For example, in hot weather, electric power generating facilities will be operating at or near capacity from approximately 3:00 P.M. to 8:00 P.M. and will be operating considerably below capacity at other times of the day. Such inconsistent energy demands cause problems for the utility companies and such problems result in higher rates for the consumer as well as possible energy curtailments.
Briefly, the fluctuating energy consumption as described above results in problems for the utility companies in that their ability to meet the demand during peak demand periods is constantly reduced as the demand for energy increases. Until recently, this presented no problems in that when the demand went up the utilities simply acquired more fuel for the production of energy or built more power generating facilities. Such solutions are no longer a simple matter due to environmental considerations, availability of fuel to distribute to consumers or to operate generating equipment, the greatly increased cost of building facilities, and the like.